Hiram Thompson was born around 1840 in Pennsylvania to John and Sarah Thompson. His father was a farmer who owned $2,790 of real estate and $615 of personal property by 1860. He grew up and attended school in Mercer, Pennsylvania, and by 1860, he was also working as a farmer.
He enlisted in the Union army on October 1, 1861, and he mustered in as a private in Company C of the 57th Pennsylvania Infantry on November 14. According to his service records, he was 5 feet, 7 ½ inches tall, with dark hair and dark eyes. The regiment took part in the Peninsula campaign, the Second Battle of Manassas, the Battle of Fredericksburg, the Battle of Chancellorsville, the Battle of Gettysburg, and the Overland Campaign. Confederate forces eventually captured him and imprisoned him at Andersonville Prison. He died of disease there in 1864.